I don’t know why the first thing I thought of when I watched this video was how cool it would be to use this stuff during a LARPing adventure, mainly because I’m not a LARPer.  But just imagine instead of throwing beanbags at each other one enterprising young wizard accountant tossing this stuff in the path of a pack of weekend goblins.  For pulling the coolest LARPing stunt ever he’d be given a plot of land next to the griffin reserve so he could build a tower from whence to practice his dark magic!

The only thing that gives me pause is that this substance, known colloquially as Pharaoh’s Serpent, and scientifically as mercury thiocyanate, is apparently highly toxic, and yet you can clearly see kids standing all around the demonstration. 
Maybe it’s only toxic when handling it.
Maybe the guy doing the demonstration is an evil wizard.